System for speed-controlled balancing the wheel of a motor vehicle

ABSTRACT

A balancing machine for balancing a wheel, wherein the wheel is rotated by a drive device for measuring the unbalance, is provided with a speed control device for controlling the speed of the drive device. The speed control device includes a computer and a frequency converter. Further drive devices can be switched by a switch-over device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a balancing machine for balancing a wheel, inparticular a motor vehicle wheel, wherein the wheel to be balanced isrotatably mounted on a shaft. The shaft is coupled with a sensor whichdetects the unbalance forces during turning of the wheel. The sensor isconnected with a computer which determines the unbalance data from theoutput signals of the sensor in conjunction with the wheel-specificdata.

2. Description of the Prior Art

A disadvantage of conventional balancing machines is that the balancingrun always takes place in the same way and cannot be adapted todifferent requirements as, for example, high balance quality or shortduration of measurement.

The disadvantage of conventional devices is the optimization ofoperation in accordance with the particular requirements, specificallybalance quality and duration of measurement.

SUMMARY OF THE INVENTION

This above-described problem is solved with an apparatus thatincorporates a drive device rotating the wheel for measuring theimbalance, and a speed control device for controlling the speed of thedrive device. The speed control device includes a controllable frequencyconverter and a computer.

Advantageous embodiments include the features of a number of drivedevices and a switch-over device being controllable by the computer foralternatively connecting the drive devices with the speed controldevice, with the drive devices being controllable by the computer withrespect to the speed control devices. In addition, a drive device foropening and closing a wheel protection bow by the motor in accordancewith the position of the wheel protection bow is used, wherein the drivedevice is controllable by the speed control device. Other featuresinclude a drive device for driving a device for determining thewheel-specific data, the drive device being controllable by the speedcontrol device; a drive device for driving a device for mountingbalancing weights on the wheel that is controllable by the speed controldevice; the speed control device being adapted to increase or reduce thespeed slowly; the speed control device being adapted to control thespeed in accordance with a selected balance quality; and the speedcontrol device having a device for monitoring the current consumption inthe drive devices so that an emergency shutdown of the drive devicestakes place when a maximum admissible current consumption is exceeded.

According to the invention, the wheel can be driven at different speedsfor the balancing run. This makes it possible to optimize the balancingrun, for example, for a short duration of the balancing process or ahigh balance quality with high measuring precision. If the duration ofthe balancing process is to be kept short, the shaft can be drivenaccording to the present invention at low speeds, which involves shortrun-up times and braking times. If the balance quality is mostimportant, however, high speeds of the wheel are necessary for obtaininga high output signal from the unbalance sensor.

In a preferred embodiment, the speed control is performed with the helpof a frequency converter.

With regard to the duration of the balancing run, the invention furtherallows in an advantageous embodiment for the wheel to be turnedautomatically (by motor) into the balancing position at the end of thebalancing run and held there for mounting the balancing weights. It isthus unnecessary to turn in the wheel manually as is done inconventional systems.

The computer-controlled speed control device can also be appliedadvantageously to other drive motors in the balancing machine, forexample for motor-driven opening and closing of a wheel protection bowor a motor-driven device for determining the wheel-specific data and/ormounting balancing weights.

In the preferred embodiment, the computer further monitors the currentconsumption of the motor or motors and switches them off if necessary.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention will be described in the following in a preferredembodiment with reference to the accompanying drawing, which shows ablock diagram of a speed control device for a balancing machineaccording to the invention.

The drawing shows computer 1 which is provided with input unit 2 andoutput unit 3. Two electric unbalance sensors 4 and 5 which are coupledwith the balancing shaft (not shown) provide their output signals tocomputer 1. Computer 1 is connected to supply voltage 13 in parallelwith frequency converter 6 and controls frequency converter 6 viacontrol line 7. A plurality of motors 8 to 11 with position indicatorsare connected to the supply voltage via frequency converter 6 andrespective switches 12. The outputs of the position indicators are fedto computer 1 via respective lines.

In the shown embodiment, a plurality of motors are parallel-connected,whereby only motor 8 serves to drive the balancing shaft. Of theremaining motors, motor 9 is provided for opening and closing the wheelprotection bow; motor 10 drives a scanning device or the like (notshown) for determining the wheel-specific data; and motor 11 is forautomatically mounting balancing weights.

In operating the output frequency, output voltage and output current offrequency converter 6 are controlled by the computer via a suitableinterface. The output of the frequency converter is switched to thevarious motors by means of suitable switch-over device 12. In this waycomputer 1 controls the speed of the motors via frequency converter 6.

When the motors are started the frequency converter is controlled insuch a way that its output frequency rises slowly, and when the motorsare braked it sinks slowly, so that a softstart and soft braking occur.The computer can furthermore control the output frequency of thefrequency converter in such a way that the balancing shaft is driven atdifferent speeds in accordance with a wavy balance quality during thebalancing run.

For turning in the wheel for mounting the balancing weights the computercontrols motor 8 via the frequency converter in accordance with theangular position of the balancing shaft in such a way that the balancingshaft is turned into the balancing position by motor and held there. Thebalancing weights can then be mounted automatically with the help of amounting device (not shown) which is driven by motor 11.

The balancing weights can be mounted sequentially, whereby the wheel isfirst turned in to a balancing position automatically and the usermounts the suitable balancing weight and confirms this to the machine.The wheel is then turned to the next mounting position automatically,etc. If the mounting of the balancing weights is also performedautomatically, the user's involvement is unnecessary.

The computer presets a maximum current consumption of the motors for thefrequency converter and constantly monitors the current consumption,whereby an emergency shutdown of the motors takes place when the maximumadmissible current consumption is exceeded.

Although the present invention has been fully described in connectionwith the preferred embodiment thereof with reference to the accompanyingdrawings, it is to be noted that various changes and modifications willbe apparent to those skilled in the art. Such changes and modificationsare to be understood as included within the scope of the presentinvention as defined by the appended claims, unless they departtherefrom.

We claim:
 1. A balancing machine for balancing a wheel, comprising:adrive device for rotating a wheel for measuring an imbalance in thewheel, said drive device including a motor and a balancing shaft; meansfor measuring the imbalance; and a speed control device for controllingthe speed of the drive device, said speed control device including acontrollable frequency converter and means for controlling thecontrollable frequency converter so as to softly start and brake thebalancing shaft and thereby control the balancing shaft at selectedspeeds, said control means including a computer.
 2. The balancingmachine of claim 1, wherein a number of drive devices and a switch-overdevice which is controllable by the computer for alternativelyconnecting the drive devices with the speed control device.
 3. Thebalancing machine of claim 1, wherein a number of drive devices withrespective speed control devices which are controllable by the computer.4. The balancing machine of claim 1, wherein a drive device for openingand closing a wheel protection bow by motor in accordance with theposition of the wheel protection bow, said drive device beingcontrollable by the speed control device.
 5. The balancing machine ofclaim 1, wherein a drive device for driving a device for determining thewheel-specific data, said drive device being controllable by the speedcontrol device.
 6. The balancing machine of claim 1, wherein a drivedevice for driving a device for mounting balancing weights on the wheel,said drive device being controllable by the speed control device.
 7. Thebalancing machine of claim 1, wherein the speed control device isadapted to increase or reduce the speed slowly.
 8. The balancing machineof claim 1, wherein the speed control device is adapted to control thespeed in accordance with a selected balance quality.
 9. The balancingmachine of claim 1, wherein the speed control device has a device formonitoring the current consumption in the drive devices so that anemergency shutdown of the drive devices takes place when a maximumadmissible current consumption is exceeded.
 10. The balancing machine ofclaim 1, wherein said control means further includes means forcontrolling the motor via the controllable frequency converter based onan angular position of the balancing shaft such that the balancing shaftis turned into a balancing position by the motor and held in thebalancing position.